Electrochemical cell with elastomeric cap

ABSTRACT

An electrochemical cell having co-axial inner and outer electrodes separated by an ion-permeable tube that defines inner and outer passageways for liquid flow lengthwise of the electrodes. The ion-permeable tube has elastomeric caps attached at each end. The elastomeric caps have rims that engage the inner walls of the electrochemical cell to separate the inner and outer passageways and the electrochemical products derived at the inner and outer electrodes.

BACKGROUND OF THE INVENTION

One use of electrochemical cells is purifying water and producing disinfecting solutions. One type of electrochemical cell that serves this purpose has co-axial inner and outer electrodes separated by a co-axial ceramic tube, all of which are fixed in opposing fittings or heads. The ceramic tube divides the cell into an anode chamber and a cathode chamber. Each chamber has a channel in fluid communication with an inlet port and an outlet port into which electrolyte is supplied and from which the resulting treated solution is discharged, respectively. In order to keep the channels of the anode and cathode chambers separate, the electrochemical cell often includes separators positioned between the inlet ports of the anode and cathode chamber as well as between the outlet ports of the anode and cathode chambers. One type of separator is installed in slots on the butt-ends of fittings and fastened to the ceramic tube. However, such a separator is difficult to install in the tight space between the fitting and the ceramic tube and there is danger of damaging the ceramic tube during assembly. Another type of separator is a plastic O-ring that is placed around the ceramic tube and that abuts the inner wall of the fittings. This type of separator is also not ideal since it does not provide optimal fitness around all types of ceramic tubes, particularly ceramic tubes having a cross-sectional configuration that is not precisely circular. Therefore, a need exists for an electrochemical cell having a separator that does not damage any components of the electrochemical cell during assembly and that has better sealing properties.

SUMMARY OF THE INVENTION

In an embodiment, the present invention provides an electrochemical cell comprising opposing first and second heads respectively having inlet ports and outlet ports and each head having an inner cylindrical wall. The electrochemical cell further provides an outer electrode secured to the opposing first and second heads and an inner electrode co-axial with the outer electrode. An ion-permeable tube is supported co-axially between the inner electrode and the outer electrode to define an inner passageway and an outer passageway. Elastomeric caps are attached to the ends of the ion-permeable tube. Specifically, the elastomeric caps have rims which engage the inner cylindrical walls of the opposing first and second heads to provide liquid-tight sealing therewith and to separate the inner and outer passageways.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an electrochemical cell according to the present invention.

FIG. 2 is a side view of an electrochemical cell according to the present invention.

FIG. 3 is a side view of an elastomeric cap according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, in an embodiment, the present invention provides an electrochemical cell 10 having opposing first and second heads 20 and 30. First head 20 has an inner cylindrical wall 35 and an outlet port 40 and an outlet port 50. Second head 30 similarly has an inner cylindrical wall 60 and an inlet port 70 and an inlet port 80. Preferably, first and second heads 20 and 30 are cup-shaped with a stepped internal diameter that defines a first cylindrical cavity part 140 and 150, respectively, into which inlet port 70 opens and from which outlet port 50 opens, respectively. Preferably, cavity part 140 and 150 lead, via respective annular end-faces 160 and 165 into respective second cylindrical cavity parts 170 and 180 of smaller diameter into which inlet port 80 opens and from outlet port 40 opens, respectively. Preferably, first and second heads 20 and 30 are each “one-piece.” As used herein, the term “one-piece” means a single solitary piece that does not have individual combinable components that can be assembled together into a single unit.

Electrochemical cell 10 further comprises an outer electrode 90 having an end 100 secured in first head 20 and an end 110 secured in second head 30. For example, cavity parts 140 and 150 can have respective recessed mouths 161 and 162 that receive respective ends 100 and 110 for liquid-tight sealing therewith. The ends of the outer electrode can be lightly machined externally over a short length (for example, 5 mm) so as to enable them to be received by the respective mouths of the cavities.

Electrochemical cell 10 further comprises an inner electrode 120 co-axial with the outer electrode 90. Preferably, electrode 120 extends axially through both cavity parts 140 and 150 and both cavity parts 170 and 180 of first and second heads 20 and 30 respectively, and has end portions 185 and 190 of reduced diameter. Preferably, ends 185 and 190 project from respective cavity parts 170 and 180 into and through respective bores 200 and 210 of respective heads 20 and 30. Preferably, there is an interference fit between end portions 185 and 190 and respective bores 200 and 210. Referring to FIG. 2, preferably end portions 185 and 190 are threaded to receive respective washers 219 and 229 and nuts 220 and 230, where end portions 185 and 190 project from respective heads 20 and 30. Nuts 220 and 230 are tightened to clamp the heads 20 and 30 firmly onto ends 100 and 110 of outer electrode 90 and to hold ends 100 and 110 firmly to inner electrode 120 with inner electrode 120 and outer electrode 90 co-axial with one another.

The outer electrode of the present invention may be a metal tube and the inner electrode of the present invention may be a solid metal rod or a hollow metal tube. The metal involved in each case may be titanium, however, where the electrode is for use as the cathode of the cell it may, as an alternative, be fabricated of stainless steel. Where the electrode is for use as an anode, it may having a coating that acts as a catalyst in the electrochemical operation of the cell, such as, for example, titanium oxide, ruthenium oxide, or iridium oxide.

Referring back to FIG. 1, electrochemical cell 10 further comprises an ion-permeable tube 130 supported co-axially between inner electrode 120 and outer electrode 90. Ion-permeable tube 130 provides an intermediate ion-permeable membrane for separating the products derived electrochemically at the two electrodes and, more particularly, divides the space between inner electrode 120 and outer electrode 90 into an inner passageway 145 and an outer passageway 155. Inner passageway 145 terminates at inlet port 40 of first head 20 and outlet port 80 of second head 30. Outer passageway 155 terminates in outlet port 50 of first head 20 and inlet port 70 of second head 30. The ion-permeable tube may be porous and in this respect may be fabricated from ceramics made from, for example, zirconium, aluminum and yttrium oxide and can contain additives such as, for example, niobium oxide, tantalum oxide, titanium oxide, gadolinium oxide, hafnium oxide and any combination thereof. In a preferred embodiment, the ion-permeable tube has the following specifications: Length (mm) 210 ± 0.5 Outer Diameter (mm) 11.5 + 0.3/−0.2 Thickness (mm) 0.7 + 0.05/−0.1 Bow (mm) ±1 Weight (g)  9.5-12.0 Materials Composition (% Mass) Alumina: 58-68 Zirconia: 27-37 Yttria: 1.3-3.3 Porosity (%) 42-62 Typical Pore Size (microns) 0.2-0.8 Three Point Break Strength, Housfield  20-100 Tensometer (N) Hydraulic Cross Flow (ml/min)  5-16

Of course, the above-listed specifications are only preferred and other specifications of the ion-permeable tube are within the scope of the present application.

Electrochemical cell 10 further comprises first and second elastomeric caps 260 and 270 attached to respective first and second ends 240 and 250 of ion-permeable tube 130. Referring to FIG. 3, first elastomeric cap 260 has tubular body 281 integral with a rim 280 and similarly second elastomeric cap 270 has a tubular body 291 integral with a rim 290. Referring back to FIG. 1, rim 280 engages inner wall 35 of first head 20 and similarly rim 290 engages inner wall 60 of second head 30. Such engagement of the rims of the elastomeric caps with the inner walls of the heads provides liquid-tight sealing therewith and separates the inner and outer passageways. Furthermore, the elastomeric nature of the elastomeric cap allows the cap to conform to cross-sectional configurations of ion-permeable tubes that are not precisely cylindrical. Referring to FIG. 3, preferably elastomeric cap 260/270 has internal sealing rings 300 which secure elastomeric cap 260/270 on the ends of ion-permeable tube 130. Preferably, elastomeric cap 260/270 is one-piece.

The extent of the projection of ion-permeable tube 130 beyond the ends 100 and 110 of outer electrode 90 within each head 20 and 30 ensures that each elastomeric cap 260 and 270 is located deeper within the respective cavity 140 and 150 than respective ports 50 and 70 so that elastomeric caps 260 and 270 maintain appropriate separation of respective ports 50 and 70 from respective cavities 170 and 180 and respective ports 40 and 80.

Referring back to FIG. 3, preferably rim 280/290 of elastomeric cap 260/270 has a length L of between about 13-14 millimeters (mm) and more preferably a length L of 13.75 mm. Preferably body 281/291 has a length L₁ of between about 12-13 mm and more preferably a length L₁ of 12.9 mm. Preferably, elastomeric cap 260/270 has a width W of between about 5-7 mm and more preferably a width W of 6 mm. Elastomeric cap 260/270 can be fabricated of any suitable elastomer such as, for example, silicone; rubber; thermoplastic elastomers such as thermoplastic vulcanizates, including polypropylene-ethylene propylene diene terpolymer; or polyurethane.

The foregoing description has been set forth merely to illustrate the invention and is not intended as being limiting. Each of the disclosed aspects and embodiments of the present invention may be considered individually or in combination with other aspects, embodiments, and variations of the invention. In addition, unless otherwise specified, none of the steps of the methods of the present invention are confined to any particular order of performance. Modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art and such modifications are within the scope of the present invention. For example, first and second heads 20 and 30 could be interchanged such that first head 20 has an inlet port 40 and an inlet port 50 and second head 30 has an outlet port 70 and an outlet port 80. Furthermore, all references cited herein are incorporated by reference in their entirety. 

1. An electrochemical cell comprising: opposing first and second heads respectively having inlet ports and outlet ports, each of the heads having an inner cylindrical wall; an outer electrode secured to the opposing first and second heads; an inner electrode co-axial with the outer electrode; an ion-permeable tube supported co-axially between the inner electrode and the outer electrode to define an inner passageway and an outer passageway, the ion-permeable tube having a first and second end; and a first and second elastomeric cap respectively attached to the first and second end of the ion-permeable tube, the first and second elastomeric cap having a rim respectively engaging the inner cylindrical wall of the opposing first and second heads providing liquid-tight sealing therewith and separating the inner and outer passageways.
 2. The electrochemical cell of claim 1, wherein the outer electrode is a metal tube.
 3. The electrochemical cell of claim 1, wherein the inner electrode is a metal rod.
 4. The electrochemical cell of claim 1, wherein the outer electrode is a cathode and the inner electrode is an anode.
 5. The electrochemical cell of claim 1, wherein the inner electrode is a cathode and the outer electrode is an anode.
 6. The electrochemical cell of claim 1, wherein the ion-permeable tube is fabricated of a porous ceramic material.
 7. The electrochemical cell of claim 1, wherein the first head is one-piece and the second head is one-piece.
 8. The electrochemical cell of claim 1, wherein the first elastomeric cap is one-piece and the second elastomeric cap is one-piece. 